Two-channel Kondo physics due to As vacancies in the layered compound ZrAs1.58Se0.39

TL;DR

This study reveals that arsenic vacancies in ZrAs1.58Se0.39 induce a two-channel Kondo effect, causing a distinctive low-temperature resistivity behavior linked to dynamic Jahn-Teller effects, and explains the suppressed superconductivity.

Contribution

It demonstrates that arsenic vacancies cause a two-channel Kondo effect via dynamic Jahn-Teller distortions, a novel insight into impurity effects in layered pnictide compounds.

Findings

Vacancies induce a T^{1/2} resistivity term independent of magnetic field.

The two-channel Kondo effect is linked to dynamic Jahn-Teller distortions at arsenic vacancies.

Superconducting T_c is suppressed due to dynamical defects in the arsenic layers.

Abstract

We address the origin of the magnetic-field independent -|A| T^{1/2} term observed in the low-temperature resistivity of several As-based metallic systems of the PbFCl structure type. For the layered compound ZrAs_{1.58}Se_{0.39}, we show that vacancies in the square nets of As give rise to the low-temperature transport anomaly over a wide temperature regime of almost two decades in temperature. This low-temperature behavior is in line with the non-magnetic version of the two-channel Kondo effect, whose origin we ascribe to a dynamic Jahn-Teller effect operating at the vacancy-carrying As layer with a C_4 symmetry. The pair-breaking nature of the dynamical defects in the square nets of As explains the low superconducting transition temperature T_{\rm{c}}\approx 0.14 K of ZrAs_{1.58}Se_{0.39}, as compared to the free-of-vacancies homologue ZrP_{1.54}S_{0.46} (T_{\rm{c}}\approx 3.7 K). Our findings should be relevant to a wide class of metals with disordered pnictogen layers.